The neural retina has a soluble 7S retinol-binding protein which was described previously (Wiggert et al., 1976). To elucidate more precisely the role of this protein in vision we examined developmental changes in the amounts of tritiated retinol bound to the 7S protein and compared these to rhodopsin levels and retinal structure in the C57BL/6 mouse. Binding of tritiated retinol by the 7S protein is not detected in retinal cytosol until the 13th postnatal day (P13). Approximately 0.4 pmoles of retinol/mg cytosol protein is bound at P13. A 6-10 fold increase in amount of retinol bound is seen over the next seven days reaching adult levels of 9-12 pmoles of retinol bound/mg cytosol protein around P40. The initial detection of tritiated retinol binding to the 7S protein does not coincide with the appearance of outer segments or rhodopsin which are detectable at P5 and P7 respectively. However, detection of tritiated retinol binding to this protein does coincide with eye opening at which time bleaching of rhodopsin occurs. The detection of the 7S retinol-binding protein at this stage of visual maturation suggests it may play a role in the cycle of rhodopsin bleaching and regeneration.